A number of different combinations of emulsified perfluorochemicals, oncotic agents, electrolytes, and nutrients will be used for the total exchange perfusion of animals. The "bloodless" animals will be further slowly perfused to keep all normal blood protein and cellular constituents at low concentrations. The perfusion will be continued for as long as possible, making modifications in the preparations as needed to maintain suitable pH, pCO2, and pO2 values, blood volume, and concentrations of important non-protein constituents. The kinds and amounts of proteins and numbers of cellular elements lost during the prolonged perfusions will be determined. Other animals will be totally perfused and then allowed to regenerate their blood cells and proteins. The kinetics of the regeneration will be studied and means of altering the regeneration rates will be sought. The metabolic and morphological integrity of the tissues of exchange perfused animals will be determined at selected post-perfusion intervals. The long term perfusion of organs in vitro will be investigated using different kinds of perfluorochemical-containing mixtures.